Momentum+Ranking+Tasks

Physics Ranking Tasks 79 Mechanics Carts and Springs—Spring Compression Time 74 The figures below depict carts moving along a horizontal surface at the speeds specified. The masses of the carts vary; specific values are given in the figures. The carts hit, compress the springs to some maximum amount, and then rebound. All of the spring systems are identical, exerting the same force on the carts, and the carts all hit the springs exactly the same way. The carts are not self-propelled, so they compress the springs for some maximum amount of time before stopping. Rank the situations in order from the greatest time of compression to the least time of compression. That is, put first the cart that takes the longest time to reach maximum compression, and put last the cart that takes the shortest time. 8 m/s 8 kg 4 m/s 12 m/s 4 m/s 12 m/s m/s 6 m/s 8 m/s 4 m/s D A B E H G C F 8 kg 4 kg 2 kg 2 kg 6 kg 6 kg 4 kg Greatest 1 _____ 2 _____ 3 _____ 4 _____ 5 _____ 6 _____ 7 _____ 8 _____ Least Or, all carts will stop in the same amount of time. _____ Please carefully explain your reasoning. How sure were you of your ranking? Basically Guessed Sure Very Sure 1 2 3 4 5 6 7 8 9 10 74 D. Maloney

Physics Ranking Tasks 82 Mechanics Bouncing Cart—Change in Momentum I 77 A cart with a spring plunger runs into a fixed barrier. The mass of the cart, its velocity just before impact with the barrier, and its velocity right after collision are given in each figure. Rank the change in momentum for each cart from the greatest change in momentum to the least change in momentum ( + direction is to the right and - to the left with –4 < -2). Before After Before After 10 kg A 10 kg 20 kg E 20 kg v o = 3 m/s v f = 0 m/s v o = 2 m/s v f = 0 m/s 10 kg B 10 kg 20 kg F 20 kg v o = 1 m/s v f = -1 m/s v o = 1 m/s v f = -1 m/s 20 kg C 20 kg 10 kg G 10 kg v o = 2 m/s v f = -1 m/s v o = 2 m/s v f = 0 m/s 10 kg D 10 kg 20 kg H 20 kg v o = 3 m/s v f = -3 m/s v o = 1 m/s v f = -2 m/s Greatest 1 _____ 2 _____ 3 _____ 4 _____ 5 _____ 6 _____ 7 _____ 8 _____ Least Or, all the changes in momentum are the same. Please carefully explain your reasoning. How sure were you of your ranking? (circle one) Basically Guessed Sure Very Sure 1 2 3 4 5 6 7 8 9 10 77 T. O’Kuma

Physics Ranking Tasks 87 Mechanics Cars—Impulse During a Change of Velocity 82 The eight situations below show before and after "snapshots" of a car's velocity. Rank these situations, in terms of impulse on these cars, from most positive to most negative, to create these changes in velocity. All cars have the same mass. Negative numbers, if any, rank lower than positive ones (-20 m/s < -10 m/s < 0 < 5). B E F O R E A F T E R A +10 m/s +20 m/s B +10 m/s 0 m/s C +10 m/s -10 m/s D +20 m/s B E F O R E A F T E R E +20 m/s F +20 m/s G -10 m/s -20 m/s H -20 m/s +20 m/s +30 m/s +30 m/s +30 m/s Most Most Positive 1_____ 2_____ 3_____ 4_____ 5_____ 6_____ 7_____ 8_____ Negative Or, the impulse on these cars is the same (but not zero) for all of these._________ Or, the impulse on these cars is zero for all of these._________ Or, it is not possible to determine the impulse on these cars for all of these._________ Please carefully explain your reasoning. How sure were you of your ranking? (circle one) Basically Guessed Sure Very Sure 1 2 3 4 5 6 7 8 9 10 82 J. Cole, D. Maloney, C. Hieggelke